Rubber tread.



PATENTED SEPT. 6, 1904.

P. W. PRATT. RUBBER TREAD.

APPLIOATION FILED 0012.3, 1903.

N0 MODEL.

Patented September 6, 1904.

PATENT OFFICE.

PHILIP W. PRATT, OF BOSTON, MASSACHUSETTS.

RUBBER TREAD.

SPECIFICATION forming part of Letters Patent No. 769,324, dated September 6, 1904.

Application tiled October 3, 1903.

i the following is a specification.

This invention relates to elastic tread or wear pieces intended chieiy for boot and shoe heels and soles and provided with relatively hard wear-resisting plugs embedded inthe elasticl body of the tread and constituting a part of the wearingsurface, all as shown in Letters Patent of the United States No. 695,298, dated March 11, 1902. In said patent the wear-resisting plug is shown as a strip of frictioned canvas or cloth closely Wound into a coil, the convolutions of which are united by coatings of rubber applied'to the sides of the strip. This plug is embedded in the central portion of the heel'and covers a considerable area of the tread-surface. Owing to its relative hardness it has been found that-the plug deprives the heel at the central portion of that degree of elasticity which is desirable.y To Obviate this difficulty, I increase the elasticity of the'rubber body over the wear-resisting plug in such manner as to compensate for the relative hardness of saidplug. I also provide certain improvements in the form of plug.

My invention therefore consists in the improvements, which I will now proceed to describe and claim.

' under side of a heel-shaped rubber tread,

showing a different construction of the wearresisting plug. Figs. 6 and 7 are enlarged Idetails of the construction of plug shown in Fig. 5. Fig. 8 represents an edge view, and Fig.- 9 a side view, of a differently-formed plug. Fig. 10 is a bottom View of aheel having a plug formed as shown in Figs. 8 and 9.

Serial No. 175,633. (No model.)

Fig. ll represents an edge view of another form of plug. y

The same reference characters indicate the same parts in `all the-figures. l

I have illustrated my invention as applied to a rubber heel, although it is not limited to this particular device and may be applied to cushioned treads for other purposes.

In the drawings, a represents the body portion, which is composed of suitably elastic vulcanized rubber.

Z) represents the wear-resisting plug, which is embedded in the under surface of the body a, the under surface of the plug and the under surface of the body being substantially iiush with each otherand constituting the tread-surface. In the construction shown in Figs. 1 and 2 the plug is composed of a strip of frictional textile fabric, preferably canvas, cut with its threads extending diagonally and coiled to form a cylindrical body or plug, as shown in the above-mentioned patent. The plug occupies the central portion of the tread-surface ofV the heel and extends lpartly but not entirely through the same, the

compensate for the relative hardness and rigidity of the plug, and thus give the heel a substantially uniform yielding quality at all parts of its tread-surface. In reducing the central portion of the heel I prefer to form a cavity c in the upper surface of the heel, said cavity having a concave surface. The cavity c is surrounded by a flat portion a', which is formed to fit closely against the part of the boot or shoe to which' the heel is attached, so that a body of airwill be confined between the central portion of the attached heel and the corresponding part of the bottom of the boot or shoe. y The elasticity of the confined air supplements the reduced central portion of the heel in giving elasticity to the treadsurface. If desired, the bottom of the cavity c may be provided with upwardly-extenda cushion above the plug ing protuberances formed to bear upon the bottom of the boot or shoe, said protuberances cooperating with the confined air in forming In Figs. 3 and 4f I show said protuberances formed as concentric rings or ridges a2, integral with the body co and separated by concentric air-spaces. It is obvious, however, that the protuberances a2 may be posts or studs separated from each other, but integral with the body a.

In Figs. 4c, 5, 6, and 7 I show the plug as composed of a series of strands l0, each of which is composed of parallel fibers of textile material. with a rubber solution prepared for vulcanization before the strands are assembled, such solution causing the strands to adhere to each other and forming a bond of union between them, which bond is rendered permanent by vulcanization. The plug thus formed is a section cut from a rope composed of strands of indeterminate length prepared and secured to each other, as above stated, said rope being cut up into sections, each of which constitutes a plug The fibers of the strands may be slightly twisted or may be straight. In the plug thus formed the threads or fibers extend substantially at right angles with the treadsurface of the plug instead of diagonally thereto, as shown in the above-mentioned patent. There is therefore less liability of the detachment of the outer ends of the threads in the form of loose hanging ends than heretofore. To increase the permanence of the hold of the rubber body on the marginal portion of the plug, I prefer to form a lip or iange b, surrounding the upper surface of the plug, said flange extending outwardly from the margin of the plug and being formed by compressing the plug before its vulcanization and while the plug is in a yielding condition. The flange is rendered permanent by vulcanization, and when the unvulcanized material of the body a is formed around the plug said material is interlocked with the flange, so that the plug' is firmly anchored in the body.

In Figs. 8 and 9 I show a plug having a series of indentations b2 formed inthe marginal portion o f one of its sides and a series of like indentations b3 formed in the marginal portion of the opposite side, the indentations Each strand is preferably coated` of one series alternating with those of the other. The indentations may be formed by compressing the portions of the plug whore the indentations occur, before the rubber is vulcanized, the plug being therefore yielding and impressionable. When the plug is incorporated into the rubber body, portions of the latter constituting projections a. enter the indentations b2 and Z13 and confine the plug in place.

The strands l() are preferably provided with cores or members l2, oflead, extending lengthwise of the strands. The ends of the lead members are exposed on the tread-surface and increase the frictional hold of the tread.

In Fig. 1l I show the wear-resisting plug provided with a peripheral groove, the sides of which form flanges or lips f If at both sides of the plug. These lips engage the rubber body which projects into the groove, so that the plug is firmly anchored in the body.

I I claim* l. A rubber tread comprising an'elastic body and a wear-resisting plug occupying the ccntral portion of the tread-surface of said body, the upper portion of the body being reduced above said plug, the said reduced portion and the plug being located relatively to each other to cause the reduced portion to con'ipensatc for the relative hardness of the plug.

2. A rubber tread comprising a wear-resisting tread-piece or plug, and an elastic body surrounding' the margin of the plug and extending across one side of the same, said body having a tread-surface surrounding the treadsurface of the plug, one or more air-chambers in its upper portion above the plug, and an air-coniining upper face surrounding the air chamber or chambers.

3. In a rubber tread, a weairesisting plug composed of parallel strands extending substantially at right angles with the wearingsurface of the tread, said strands having lougitudinally -eXtending members or cores of lead.

In testimony whereofl I have affixed my signature in presence of two witnesses.

PHILIP W. PRATT. vWitnesses:

C. F. BROWN, E. BATCHELDER. 

